1. Field of the Invention
The present invention relates to a web winding method for winding a plurality of cut webs into a roll shape while being pressed by rider rollers.
2. Description of the Related Art
Recently, in a method for winding a cut web, taking as an example a surface winding method, a winding core is retained by two long surface drums (drive rollers), and a single rider roller, which is of the same length as the surface drums. While being gripped between the surface drums and the rider roller, when a rotary drive force is applied thereto, a plurality of small-width webs, which are cut by a cutting process and fed, are wound on the winding core. (See, Japanese Laid-Open Patent Publication No. 62-116448.)
In general, a wide raw fabric web has a thickness (thickness variation) that differs in the widthwise direction. For example, per 100 mm in a widthwise direction, a difference in thickness exists on the order of several μm. When a raw fabric web having such thickness variations in the widthwise direction is cut and each of webs, which are small in width, are wound simultaneously, the difference in thickness accumulates, and a variance in the winding diameters of respective webs occurs.
During winding of the webs, in the case that the winding diameters are different between plural webs as noted above, a difference occurs in the pressing force on each of the webs imposed from the surface drums and the rider roller, and as a result, differences can occur in the winding stiffness among each of the webs. In the event that differences in the pressing force are especially large, problems occur in that wrinkles may result in webs for which the winding stiffness is excessively strong, or winding looseness may occur in webs for which the winding stiffness thereof is insufficient.
Consequently, conventionally, the rider roller is divided into a plurality of divided rider rollers, the widthwise dimensions of which are smaller than the width of the cut webs. The respective divided rider rollers are sequentially arranged roughly coaxially at a given gap pitch, which is less than the width of each of the webs, each of the divided rider rollers being moved mutually independently in the pressing direction, whereby the respective webs are pressed thereby (see, for example, Japanese Patent No. 2678826 and Japanese Patent No. 3539786). Owing thereto, because the pressing force of the divided rider rollers with respect to each of the webs is averaged, differences in winding stiffness between respective webs does not occur. Accordingly, even if differences in the winding diameters between each of the webs occur, fear of wrinkles or poor performance due to excessive winding stiffness in a portion of the webs, or winding looseness caused by insufficient winding stiffness, can be eliminated.
Further, as a method for winding a material used for inkjet recording, there is known a method as disclosed in Japanese Laid-Open Patent Publication No. 2002-265106. With this method, the pressing force of a rider roller is regulated so as to reside within a range of from 5 to 40 kg per each one meter web width of the inkjet recording material. In this case, the inkjet recording material can be wound without decreasing the gloss (luster) of the inkjet recording material.
In the methods of Japanese Patent No. 2678826 and Japanese Patent No. 3539786, from the fact that a plurality of divided rider rollers are arranged with respect to a single web, when directed to winding of an inkjet recording material for example, if the pressing force of the divided rider rollers simply is increased, within the surface of the web, recesses occur at portions where the divided rider rollers press against the web, and boundaries (planar unevenness) with portions that are not pressed occur, which can be recognized by the naked eye. In such a case, the appearance thereof becomes unsatisfactory and the web cannot serve as a product.
Further, in the method of Japanese Laid-Open Patent Publication No. 2002-265106, and similarly in the disclosure of Japanese Laid-Open Patent Publication No. 62-116448, because winding is carried out while the webs are pressed by a single rider roller, when there are thickness variations in the widthwise direction of the raw fabric web, there are problems in that wrinkles in the web or looseness in the web windings tend to occur. In particular, there are further problems in that, at both ends of the web, winding portions become gradually expanded out toward the center, and shifting between the windings (telescopic winding) is generated.
Consequently, although it might be considered as a way of resolving the aforementioned problems to apply the divided rider rollers of Japanese Patent No. 2678826 and Japanese Patent No. 3539786 to the method of Japanese Laid-Open Patent Publication No. 2002-265106, because a large number of divided rider rollers are arranged, due to the fact that the width of the individual divided rider rollers becomes smaller, the pressing force produced thereby increases, and planar unevenness occurs. Further, if the pressing force is decreased in order to avoid such planar unevenness, there is a problem in that shifting between the windings easily occurs. Additionally, because the region of stability (stable operating region) thereof is narrow, there is a concern that manufacturability is decreased.